Mumbaistatin is an aromatic diketo derivative which, as glucose 6-phosphatase translocase inhibitor, can be used in the treatment of diabetes mellitus. Mumbaistatin (A) can be isolated from the microorganism DSM11641 (Vertesy et al., WO99/67408 and J. Antibiot. 2001, 54, 354-363). WO01/30736 describes the mumbaistatin derivatives (B)-(D) and esters and ethers thereof. Mumbaistatin is present in an equilibrium of an open form (A) and a hemiacetal form (B) and, depending on the pH, can be converted into the compounds (B) and (D).

Krohn et al. (Tetrahedron 2006, 62, 1223-1230) describe a 7-9-step synthesis of the tri-ortho-substituted 2′-dealkyl mumbaistatin derivatives of the formula (E), where the oxidation of the benzylic position was effected using Br2 in a CCl4/water mixture with irradiation
and where the anthraquinone skeleton is constructed by a multi-step aldol condensation of a diene intermediate prepared by a Lewis acid-catalyzed Michael addition, and the total yield starting from the naphthyl derivative (F) is from 2.8 to 14.1%.
Kaiser et al. (J. Org. Chem. 2002, 67, 9248-9256; Tetrahedron 2003, 59, 3201-3217) describe the 9-step synthesis of the tri-ortho-substituted 3′-deoxy-2-decarboxy mumbaistatin derivative (G),
where the anthraquinone skeleton (H) was prepared via an aryne/phthalide anellation and the total yield starting from commercially available 3-hydroxybenzaldehyde is 3.7%.
It is the object of the present invention to provide an efficient synthesis route to mumbaistatin derivatives.